A good post flop player does 2 things:

#1 he is more observant than his opponents and therefor picks up more small tidbits of information.

#2 with this extra information he will make more correct decisions in borderline situations.

Think about this way;

a 20/40 limit player who makes 2 extra value bets in a 4 hour session, could go from being break even to winning $20 an hour!

a 1/2 NL player who correctly lays down a hand or picks off an extra bluff could do the same.

Basically what I'm saying is, the difference between a winner and a loser is pretty small. And, it usually involves small edges post-flop. Unfortunately those small edges only come through hard work and focus.